Although it's pegged as a 3D graphics framework for the browser, could Google O3D be used as an RIA framework similar to GWT, Flex or Rails?
Short answer:
Yes.
Long answer:
More likely it'll just be used for in-browser games. It takes a lot of work to build a decent RIA framework on top of a 3d framework, and it's unlikely such a framework (if it's ever released) will be very developer friendly.
If you want good a RIA framework look at Silverlight or Flex.